I wanted to post something positive online about my recent experiences with NextGen. The 3.5KW generator installed by the original owner in 2004 became a victim of neglect. The original heat exchanger developed a leak, and lost a lot of coolant. There was also a raw-water leak in the exhaustelbow. The second owner used the genset a lot, because they kept the boat on a mooring. We have always been at the dock, so mostly ran the generator to make sure it still worked since we haven't been cruising overnight since we bought our boat in 2014. Because the generator was in a fiberglass enclosure, the only way to check the coolant level was to remove the cover, which was complicated by the design of the cabinet from the initial installation. There was a screw-off port that allowed access to the oil filler and dipstick, but the only way to inspect coolant was to see if the overflow reservoir still had some in it. Needless to say, when I discovered that the generator was shutting itself down for an overtemp condition, I started digging with our local mechanic and we discovered the leaks. First, we replaced the impeller, which is an over-the counter Jabsco part, and easy to find. When that didn't solve anything, we pulled the HE and found it was leaking at the end caps. I called Ken at NextGen, explained what was going on, and drove from Brunswick to Jacksonville to get an new heat exchanger assembly, gaskets, studs and screws. Ken agreed that the old HE was shot, probably because the zinc had not been replaced (although there was one in the ship's spares kit). The new HE is from a newer supplier, and a solid bronze casting with brass end-caps and o-rings. It's a much better design. IMO. I tried to install it myself, but it wouldn't seal. I called Ken, who suggested that the mounting adapter may have warped from the heat, and went down to pick up a new one. He threw in a new gasket and hardware. When we went to install it, though, my mechanic found a couple of spider cracks starting in the base of the HE casting. running from the corners to the bolt holes. While not completely cracked through I made another run to Jax to show them the areas of concern. They replaced the heat exchanger, no questions asked. After another installation attempt with a new gasket, we had some coolant weeping around the bolt holes. More troubling was the raw water leak, caused by the fact that the fiberglass portion of the exhaust was being eaten away by contact with the enclosure. I took the lower part of the exhaust back to NextGen, and purchased an complete new exhaust. The threw in another gasket, some additional mounting hardware, and all the hoses I needed to do the job. I took my wife on the drive down, and they took their time to explain a lot about their product to her and didn't rush us out. Yesterday, finally, we got everything to mount up and NO MORE LEAKS! The generator runs great, and puts out good power.

So kudos to the guys at NextGen-- they took an interest in helping me solve the problems with my generator, they admitted that sometimes they get a bad part from a vendor, they replaced it without any fuss, and made sure i had the parts to do the job. They don't do a lot of online advertising or social media, so they rely on satisfied customers to share their experiences. I thought their support was good. As Ken said, if you have a problem, just call-- they will walk you through it!

That is low hours for a 12 yr old generator.
I have heard the Achilles heel of the older ones was the exhaust elbow, it could wear and allow water into the exhaust valve.
New exhaust is wrapped in high temp insulation, and the water is injected further down stream I believe preventing this.
Yours is the first heat exchanger problem I have heard of. Others have said a spare water pump is good to have, but as you say it's a standard pump.
I believe Nexgen has a "cruisers spares" kit they sell ?

I have a 3.5 myself is why I am so curious, want to know what to watch for.

That is low hours for a 12 yr old generator.
I have heard the Achilles heel of the older ones was the exhaust elbow, it could wear and allow water into the exhaust valve.
New exhaust is wrapped in high temp insulation, and the water is injected further down stream I believe preventing this.
Yours is the first heat exchanger problem I have heard of. Others have said a spare water pump is good to have, but as you say it's a standard pump.
I believe Nexgen has a "cruisers spares" kit they sell ?

I have a 3.5 myself is why I am so curious, want to know what to watch for.

Sent from my iPad Pro using Cruisers Sailing Forum

Mine did come with the later exhaust. I believe that most of the problems were caused by not replacing the zinc, running it without enough coolant, and possibly a failing impeller. Probably warped the old copper-nickel HE and adapter plate to where it would longer hold a seal. We made sure that the hose on the outflow side of the fiberglass exhaust piece was helping shield the glass from vibration damage. But if you have the enclosure, that would be a good thing to check periodically.

Whoever did the original install made it nearly impossible to work on the genset. We corrected that by making the upper panel of the cabinet around the generator easier to remove. Also added an upper inspection port to get access to the coolant cap without removing the fiberglass enclosure.

As you mentioned, probably a good idea to carry a spare water pump, impeller, and belt. Those would be really easy to replace while under way.

The engine itself is pretty rugged. I think if you pay attention to cooling and make sure the wet exhaust is tight, you'll be OK.